Drainage system



Sept. 20, 1949. w. KJELLMAN DRAINAGE SYSTEM Filed Jan. 22, 1948 Illa vPatented Sept. 20, 1949 v#inwinnen SYSTEM Walter Kaliman, stockholm,smear Application January 22,

194s, .ser-iai No.. 3,1 1c

In Sweden December I2, 1945 Section-1, Public' Law ugust-'llig Patent'expires Decemb'erfIZ; E965- 10 Claims.

This application is a continuation in part replacing. my" copendingapplication Serial No. 636,41,.led December 21, 194:5 now'abandoned",and, as to all common subject matter, relates backl toy said applicationSerial No.- 636,416,V and to'` foreign applicationsT correspondingthereto for all dates and rights incident tothe lingthereof;

present invention relates-to a drainage system. In. my: oopendingapplication? Serial No; '762,946,1I1havesuggested` to reduce 7,thepercentage of'waterin'clay grounds' and similar groundsby the'arrangement oi'vertical band-shaped'fdrains n1l the ground,v saiddrains-being made from a materiak pervioustolwater. The drainsfacilitate the' escape of, suchpore Water as is being squeezed out ofthe ground bythe load that is applied-.- on the ground surface; Thus,the consolidation of the ground is accelerated, the purpose being toincrease the carrying capacity of the' ground' and/ or to acceleratesettlements. There is a twofold purpose of the band or strip-shape ofthe drain, firstly to# reduce the amount of drain material in relationto the area of ciontactbetweenV drain and soil, l the draining effectbeing dependent mainly on. the: size of said area, and, secondly, torender the drain flexible so that it can be'rolled on a drumv and easilytransported and handled.

The material ofr said drains must be very porous, and the pores must belarge, .inorder that the permeability of the drain-.to water shallbesufficient in theflongitudinal directionthereof.. FurthermorathemateralmustI be capableof withstandingthe horizontal earth pressure withoutloosing too much ilo-permeability. Finally,`even very small. soil4grains .must be prevented fromenteringthepores of the material, becausethey cou-ld clog there, thus reducing the permeability of the drain. Incertain cases it has been found diicult to answer all oi theserequirements- It is the object of the presen-t inventionto. pro- Videband-shaped draining means. which are capable of withstanding the earthpressureand into which soilgrai'ns cannot penetrate, while the drainingVmeansyet have suicient permeability.

In the drawings: Y y l Y Fig. 1 is a horizontal sectional Viewsubstantially at' right' angles' to the longitudinal direction of adrain and' showing one form of the invention Fig. 2 isa horizontalsectional 'View of a modi'- ed form of the invention; y

Fig. 3 is a verticaly section oi part of a drainage' system comprisingdrains of the type illustrated in Fig. l or Fig'. 2, the drains beingshown in sections along thek line III-III'in Fig. 1 or Fig; 2';

Fig. 4 is a horizontal section of part of another embodiment oftheinvention;

Fig. 51 is a vertical section taken on the line. V-V of Fig'. 4'; and 1'Fig. 6 is a similar vertical sectionalview of a.: slightly modifiedembodiment of the; invention.v

While the drain according tof the inventionmay have' any suitable'croSsLsectiong. I. have illus.'- trateds-by of example,l some drains ainrrovrY substantially rectangular cross-section eac Y v Thedrainaccording to Fig. lfismadeby1 tastening twostrip'or band-shapedlayers-l and 2. oli a: uniform width. together, the' surface ot the onelayerl iacingthe other layer 2.-' being i channelled inthe longitudinal'direction oi.- the drain.- VThe channels Aform internal passages;3ffinthe` drain, the twoflayers. bearing; oneacim other at the:proiectionsd.' Y 1 According to the.- embodiment shown in-Fig.. 2; thedrain cons-istsoi three layers',L the outer: lay.- ersfb and l-ybeingof` a, material Apervionsi to'v water. and capab1le of. preventingvfine soilgrainstrOm passing: therethrough,. iwhereasthew intermediatelayer averygreat fperrneability4 in theflongitudinal, directionoaf.. thedrain and is'able to withstand the horizontal@ earth. pressure,Atransmitted by the outer layers, Without-loosirz; too nmcth ot itspermeability; In the example; illustratedY in Fig.. 2, stripsor bars 5are suitably spacedeinparal-lel-between two non-channelled; layers 6and. 1f, and the whole. structure Vis fastened together-so; astufo-:n1xlongitudinal passages. 3. K t The fastening may be eiected by gluingalong the two edges of the drain ,and-,.ifstrips-or barsi are used, atindividualfpointsf in :the interior oi, the drain. Y Instead of gluing.,clampingiory sewing may be used..

Laboratory innestigationsi have shown that the drains may beY made. ofordinary,unsized4 cardboard.- or similar flexible materials. They aremade, vr-for instance, of. ath-icknessoi one eighth oi an inch` and on awidthof-four. inches with pas-- sages `ofthe crossfsection 1*/25 :e1/z5inches atl-mutual-.distances of one fifth` of aninch,V and, the length.oi.' each. drain may amounttoffor instance, 5 to 60 feet. 5

, -In Fig.. 3 I haveshown a section ot adrainage system.YWith-substantially vertical.: drains A, B,y and C in their positionsin`aground 8 the sur.- fae of. which. is indicated at.Y `For the. sake ofclearness, the thickness-of` the.v drainsgis exaggerated` in.l thisligure. According-.to the peizmeability andreompressibility of theandthe widthand permeability of.` thedrain, andthe rate at which theconsolidation. of the soil isA wanted to take, place, the spacingd; ofthe drainsfA-B,. C is calculated theoretically.. It may vary, forinstance, between 3 and 10 feet butshould.- be the same, or: nearly thesame, inthe planeet Fig 3`v as the: direction perpendicular thereto..Aswill. be seen from. Fig. 3,A the upper ends of the drains are shghtlyprojecting above the suriace l1 oi they ground, while the lower endsofthe drains are terinitiating in thevground. rfla-layer t0 consisting oSandor gravelgifs placeduponithge.k surface 3;, the

3 height of said layer being somewhat greater than the height of theprojecting portions of the drains. Resting on the layer I0, there is adiagrammatically indicated embankment II, such as for a highway or arunway for airplanes, exerting a vertical load on the ground 8.

Any suitable means may be used for driving the drains into the ground,an appropriate device for that purpose being described in my above namedapplication Serial No. 762,946.

The material of which the drains consist should be pervious to water,but the pores must be relatively s-mall so as to prevent earth fromintruding the drains and obstructing the ilow of water.`

In cases where the earth pressure on the drain is very great, it isnecessary, for the purpose of preventing a collapse of the passages, toincrease the strength of the drain material in a wet state, Which iseffected by suitable impregnation. It should then be attended to,however, that the permeability of the drain material is not impaired toomuch. Further, the drain should be compressible in the longitudinaldirection so as to be able to take part in the vertical compressionofthe ground without being damaged.

- From any point of thesurrounding earth, the water squeezed out by theload flows approximately perpendicularly to the nearest drain, asindicated by the arrows in Fig. 3, and enters the passages 3. Sincethere is no outlet at the lower end of the drain, the water travelsupwards in the passages 3 and, at the upper end of the drain, enters thesand r gravel layer lil. In this layer, the water liows laterally untilbeing caught by a suitable surface drainage system, if any, not shown inthe drawing, or else it` flows out from under the embankment.

Laboratory tests have proved that the permeability in the longitudinaldirection of a drain according to Fig. 2 is surprisingly gre-at ascornpared with that of a drain without passages. Thus, thanks to theprovision of the passages, the spacing: of the drains can be increased,which, of course means economy.

Another embodiment is shown in Figs. 4 and 5 wherein the drain consistsof a single 'stripV or band I2 of a flexible material pervious to waterand a passage or tube I3 arranged outside the edge of the strip. Thepassage is formed by a wire helix I4 which is retained in position bymeans of a. securing strap I5 attached to the band, said strap alsopreventing the `earth from penetrating into the helix and in between thehelix and the band. The passage I 3 is open at its top and terminatesnear the surface of' the ground.

If the band material is of inferior strength in a wet state, it ispossible to prevent the same from penetrating into the helix by the edgeof the band facing the helix being lined with a filtering strip I6 fromfabric or some other suitable material pervious to water, the filteringstrip being retained in position by the securing strap I5. The waterentering the band I2 from the surrounding earth will ow into the passageI3 substantially in the direction of the arrows shown in Fig. 5 and willthen continue to flow upwardly through the passage.

If desired, the wire helix may be made fromV other material than metal,and it may also beY replaced by a perforated tube, consisting, forinstance, of network, as shown at I 4a in Fig. 6. The securing strap I5may consist of fabric, cloth, water-proof paper or the like, and it maybe secured to the band such as by sewing, past- .4 ing or stitching. Theband may consist of any suitable number of layers. If required, thedrain may be provided with a passage at the other edge as well. One ormore .passages in the interior of the drain are also conceivable, eachof Isuch passages being provided with a wire helix or the like, the samebeing :covered by a lter, if de- 'sired.

As will be seen from Figs. 1 and 2, the passages 3 are arranged relativeto the appertaining strip or band so that parts of said strip, as viewedat right angles to their surfaces, are free from passages. As theseparts are more rigid against the earth pressure than the parts traversedby passages, the earth pressure will distribute itself unevenly and begreater at the first-named parts than at the latter parts. Thus, to acertain extent the soil itself will bridge over the parts traversed bypassages.

The longitudinal passage or passages in the drains may obviously beprovided by means other than those shown and described by way ofexample. The invention is obviously not limited to a plurality ofpassages in the drains.

While in the foregoing description I have confined my consideration tovertical drains, it will be understood that the invention is notconfined to exactly vertical drains andpassage means, but may equallywell beV embodied by the use of drains having passage means located atan acute angle with respect to the surface of the ground, for instance,between and 45.

What I claim is:

1. In a drainage system for accelerating the consolidation of groundshaving a very low permeability to water, a plurality of laterallyinterspaced drains placed in the ground, each of said drains comprisinga exible strip exerted to lateral earth pressure and consisting of amaterial pervious to water, and said strip having passages extendinglongitudinally of the drain and opened at the outer end thereof topermit water squeezed out of the surrounding earth through said strip toflow through said passages.

2. In a drainage system forl accelerating the consolidation of loadedgrounds having a very low permeability to Water, a plurality oflaterally interspaced drains placed in theground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, and substantially'verticallyextending passages in said strip, said passages being open at their topsand terminating near the surface of the ground, whereby to permit watersqueezed out of the surrounding earth through said strip to flow upwardsthrough said passages onto said surface, said passages being arranged insaid strip so that parts of said strip, as viewed at right angles to thesurface of the strip, are free from passages.

3. In a drainage system for accelerating the consolidation of loadedgrounds having a very low permeability to water, a plurality oflaterally interspaced drains placed in the ground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, said strip comprisingband-shaped layers fastened to each other, the surfaces of said layersfacing each other having different geometric shapes so as to providesubstantially Vertical internal passages therebetween, said passagesbeing open at their tops and terminating near the surface of the ground,whereby to permit watersq'ueezed 'out f the sur i rounding earth throughsaid strip to ow upwards through lsaid passages onto said surface.

4. In a drainage system for accelerating the consolidation of loadedgrounds having Ya very low permeability to water, a plurality oflaterally interspaced drains placed in the ground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, said strip consisting ofthree layers, the outer layers being of a material pervious to water andcapable of preventing fine soil grains from passing therethrough, andthe intermediate layer having a great permeability in its longitudinaldirection and being adapted to withstand the horizontal earth pressure,transmitted by said outer layers, without loosing too much of itspermeability.

5. In a drainage system for accelerating the consolidation of loadedgrounds having a very low permeability to water, a plurality oflaterally interspaced drains placed in the ground, each of said drainscomprising a ilexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, said strip comprising threeinterconnected band-shaped layers, the intermediate one of said layersconsisting of interspaced bars so as to form substantially verticalinternal passages, said passages being open at their tops andterminating near the surface of the ground, whereby to permit Watersqueezed out of the surrounding earth through said strip to flow upwardsthrough said passages onto said surface.

6. In a drainage system for accelerating the consolidation of loadedgrounds having a very low permeability to water, a plurality oflaterally interspaced drains placed in the ground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, and a flexible perforatedtube extending substantially vertically and secured to an edge of saidstrip, said tube being open at the top and terminating near the surfaceof the ground, whereby to permit water squeezed out of the surroundingearth through said strip and entering said tube to flow upwardstherethrough onto said surface.

7. In a drainage system for accelerating the consolidation of loadedgrounds having a very low permeability to water, a plurality oflaterally interspaced drains placed in the ground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, and a wire helix forming aflexible perforated tube extending substantially vertically and securedto an edge of said strip, said tube being open at the top andterminating near the surface of the ground, whereby to permit watersqueezed out of the surrounding earth through said Strp and enteringsaid tube to flow upwards'therethrough onto said surface. Y

8. In a drainage system for accelerating the consolidation of loadedgrounds having a very low permeability to water, a plurality oflaterally interspaced drains placed in the ground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, and a flexible networkforming a perforated tube extending substantially vertically and securedto an edge of said strip, said tube being open at the top andterminating near the surface of the ground, whereby to permit Watersqueezed out of the surrounding earth through said strip and enteringvsaid tube to flow upwards therethrough onto said surface.

9. In a drainage system for accelerating the consolidation of loadedgrounds having a very low permeability to water, a plurality oflaterally interspaced drains placedy in the ground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to water, a flexible perforated tubeextending substantially vertically and secured to an edge of said strip,said tube being open at the top and terminating near the surface of theground, whereby to permit water squeezed out of the surrounding earththrough said strip and entering said tube to flow upwards therethroughonto said surface, and a layer of a material pervious to water betweensaid strip and said tube.

l0. In a drainage system for accelerating the consolidation of loadedgrounds having a very low permeability to water, a plurality oflaterally interspaced drains placed inthe ground, each of said drainscomprising a flexible strip exerted to lateral earth pressure andconsisting of a material pervious to Water, a flexible perforated tubeextending substantially vertically and secured to an edge of said strip,said tube being open at the top and terminating near the surface of theground, whereby to permit water squeezed out of the surrounding earththrough said strip and entering said tube to flowY upwards therethroughonto said surface, and a longitudinal strap pervious to water, saidvstrap surroundingsaid tube and being secured to said strip.

WALTER KJ ELLMAN.

No references cited.

